1. Field of the Invention
The present invention relates to a rolled strip shape detecting device, and more particularly to a device for detecting a shape of a rolled strip with a higher accuracy by compensating a shape detection error of an actual strip as generated because of deflection of a roller caused by tension of the rolled strip and tare of the roller.
2. Description of the Prior Art
Generally, in producing a rolled strip such as a steel strip or a nonferrous metal strip such as an aluminum plate or foil, it is necessary to detect a shape across the width of the rolled strip rolled by a rolling mill. It is known that means for detecting the shape of the rolled strip across its width is provided downstream of the rolling mill.
FIG. 7 shows a schematic illustration of a conventional shape detecting device for the rolled strip. A shape detecting roller 3 is provided between an outlet of the rolling mill 1 and a strip winding reel (winder) 2 in such a manner as to contact a rolled strip 4. A detection signal of strip shape as detected by the shape detecting roller 3 is fed to a signal processing computer 5. After being processed by the computer 5, the strip shape is indicated by a shape display panel 6 connected to the computer 5.
In particular, as shown in FIG. 8, the shape detecting roller 3 is of a division type such that a plurality of discs 7 are axially stacked to be united as an integral roller.
Each disc 7 is provided with a sensor 8 for detecting a radial load applied to the outer peripheral surface of the disc contacting the roller strip. A distribution box 9 is provided at one end of the shape detecting roller 3, and a rotation transmitter 10 is interposed between the shape detecting roller 3 and the distribution box 9. Detection signals from each sensor 8 are transmitted through the rotation transmitter 10 and the distribution box 9 to the computer 5.
Thus, the load applied across the width of the rolled strip 4 is measured by each sensor 8 in the discs 7 of the shape detecting roller 3. Then, the strip shape across the width of the rolled strip 4 is calculated by the computer 5 according to the detection signals from the sensors 8, and is indicated by the shape display panel 6.
Further, although not shown, the shape signal of the rolled strip 4 is also outputted from the computer 5 to any control system for the rolling mill 1.
However, generally in the shape detecting roller for the rolled strip, the axis of the shape detecting roller 3 formed by the plural discs 7 is deflected by the tension of the rolled strip 4 and the tare of the shape detecting roller 3 as shown in FIG. 9.
Because of such deflection, a distance L.sub.i from an output end A of the rolling mill 1 through the outer periphery of the shape detecting roller 3 to a take-up point B of the winding reel 2 at various transverse points of the rolled strip 4 (L.sub.i corresponds to the disc 7 placed at the number of i counted from a transverse end of the strip) is rendered smaller than a distance L similarly measured at a bearing portion of the shape detecting roller 3. In the conventional device, such error in the distance is not accounted for, and the strip shape is therefore computed in such a manner as if the central portion across the width of the rolled strip were extended.
For example, letting the minimum distance at the transverse central portion of the rolled strip 4 denote L.sub.min and the maximum distance at both the transverse ends of the rolled strip 4 denote L.sub.max, there is generated a maximum detection error .epsilon.=[(L.sub.max -L.sub.min)/L.sub.max ].times.10.sup.5 [I-Unit] in the conventional shape detecting device which takes no account of the deflection of the shape detecting roller. That is, the value of an actual shape +.epsilon.[I-Unit] is detected at the central portion of the rolled strip 4.
While the shape detection error of the rolled strip 4 due to the deflection of the axis of the shape detecting roller 3 in a low-tension shape detecting device (under a tension value of about 1-2 ton, for example) occupies a relatively small proportion of the whole error, the shape detection error due to the deflection in a high-tension shape detecting device for a high-tension thin sheet rolling mill, for example, occupies a considerable proportion (about 20-50%) of the whole error. In this manner, the error due to the deflection of the shape detecting roller 3 generated by the tension of the rolled strip 4 and the tare of the roller 3 is included as it stands into the detection output from the shape detecting device, causing a reduction in detection accuracy.